Some examples of small telephone systems have been generally referred to as key telephone systems. Traditionally a key telephone system is provided by extensive telephone line and control lead wiring between key telephone sets. Each key telephone line extends to a telephone exchange. Each of the telephone sets includes a plurality of push button switches or keys, each for connecting the telephone set to a particular telephone line among a plurality of telephone lines routed to the key telephone set. The switching function of line selection is mechanically provided and distributed among the key telephone sets. Any features in addition to plain ordinary telephone service (POTS) must be added on a per line basis. The primary advantage of these systems is economy with small size. However, if such a system is required to expand along with the organization it serves, over a time it eventually becomes more expensive on a per line and feature basis than a private branch exchange would be. Key telephone systems are also characteristically of the analog signal type, and therefore are impractical to interface with an ISDN as will likely be desired by business customers in the near future.
So far as those aspects of the invention concerned with replacement and/or relocation in telecommunications systems generally are concerned, most telephone sets or other terminal apparatus nowadays are connected into the system by jacks, so it is a simple matter for the user to unplug a terminal apparatus and reconnect it at a different port. Of course, if those attributes of the terminal apparatus not resident in the terminal apparatus itself are to be retained, corresponding administrative changes must be made at the switch or, in the case of a key telephone system, at the key switch unit. Existing systems require the intervention of a skilled craftsperson to effect such changes, typically by locating the feature set of the terminal apparatus at the vacated port and assigning it to the new port. This involves high costs and may incur delays. A similar situation arises if the user replaces the terminal apparatus with a new set i.e. new to the system rather than being relocated from another port. Usually this would be done to replace a defective set. Providing that they are of the same type, the new set will need to inherit the old set's administration data and, where applicable, intercom number.
So far as those aspects of the system which concern provision of features on demand are concerned, in such systems, various features may be made available to the user. For example, Automatic Call Distribution is a feature which routes incoming external calls, on a first come, first served basis, to the first available terminal. Such a feature finds application in airline reservation systems, telemarketing, customer service, and so on.
Least Cost Routing is a feature which automatically routes outgoing calls using the least expensive route. For example, during business hours, outgoing calls may be routed over tie lines. After the time when lower long distance rates come into effect, calls to the same destination may be routed over regular central office lines. With such a feature, the user need not worry about which line he should use, but simply dials the number and the feature makes the decision for him.
Implementation of such a feature involves the execution by the user's terminal of a predetermined set of functions, each of which may comprise a number of specific steps.
In conventional systems, software for implementing such features is resident in the core or central processor which serves all of the terminals. If a user requests a different set of features, a craftsperson must access the core processor and make the necessary changes. Likewise, if new features become available, the craftsperson must access the core processor to install them.
The core processor is a critical part of such a system so any mistakes when making such alterations could have serious repercussions.